Shadow, I'm well aware that the output from solar PV and wind is less stable than from fossil fuels and nuclear. But that doesn't equate to network instability; it merely introduces technical problems that will have to be overcome. And they can be overcome. But people like you seem to treat every technical problem as an insurmountable obstacle!

Secondly, where did you get the ridiculous idea that solar and wind power have maintenance costs comparable to the fuel costs of fossil fuel power? They're designed to be low maintenance.

Thirdly, although SA is not a country, it has more people than Estonia and is bigger than any country that's entirely within Europe. Claiming "if all its generation failed, it would simply draw off the Aus network" shows a very poor understanding of the situation: SA only has two connections to Victoria. There's no direct connection to the NSW or Queensland grids, and no connection at all to those of WA or the NT. Around the turn of the millennium, before SA's wind turbines were built, SA had frequent brownouts and had to resort to load shedding.

Fourthly, the current practical limit of 30% wind and solar is a figment of an imagination so limited it can't even comprehend technical problems being overcome!

Finally, load shedding is not demand management, it's failure of demand management: the demand still exists but is unsatisfied. Most customers have no means of regulating load YET, but that's something that could easily change in the future. The cost of shutting plant varies a lot - it can be high or it can be very low (air conditioning being an example of the latter). And a primitive form of demand management has been in operation for years, with some equipment automatically taking advantage of the cheaper electricity after midnight. Why do you imagine we can't do this in real time?

Aidan,

Just an idea you should be interested in.

I would like to paint a picture. It has been an extraordinary hot day and the slightly cooler evening is coming, but no promise of anything but the mildest hot sea breeze. Still 40 degrees, with the sun setting in the west. An intense high system over eastern Australia promises more of the same tomorrow, another typically summers baking day. Back in the 2010's the so called Environmentalists had finally got their way and most base load coal generators in Australia had been closed. Australia was relying on renewable energy, and the Environmentalists were ecstatic. Hundreds died that night, the elderly in their homes, hospital emergency departments collapsed as they who could not call on reliable base load electricity. Backup batteries were exhausted, and little power was available for emergency power. The electrical distribution
system collapsed, and stayed collapsed.

The above scenario just could not happen, could it?

Aidan, It does not matter how many overbuilds of the electrical generating system in renewable energy it will ALWAYS need almost 100% backup so do not build it. In 2014 South Australia lost 28.9% of its wind power in a 5 minute period. Building renewables is just crazy stuff.

Graeme
The only case that can be made for Australia to go nuclear is to reduce CO2 emissions, if you don't accept that is necessary then there is we have no reason to go nuclear, even using the most favorable figures, and making highly optimistic assumptions nuclear would be 2 or 3 times more expensive than coal in Australia. I don't happen to think that there is any good argument to go nuclear in Australia as we have plenty of potential to use premium sites for renewables at a lot less than the real cost of nuclear.

One of the great advantages of wind and PV solar in Australia is the fact that they don't need water to run them and we are going to need to save every drop of water we can because of the increasing population, plus rain fall trends in south east Australia have been in are steady decline for the last 30 years.

Bazz
The proportion of renewables used in Germany is 23% not 60% and at the present they are increasing their use of coal but of course because German power prices are high and rising it must mean renewables are a bad idea go figure !
It is just possible it has something to do with the fact power is taxed at 56% in Germany and they have closed down a load of nuclear power plants well before their use by date.

I don't think you guys have any idea just how interconnected the European grid is, in fact Germany is a net exported of power. Hover the mouse over the countries you are interested in.

http://www.energy-charts.de/exchange.htm

Graeme
The hottest conditions in South East Australia occur under very favorable conditions for renewables when skys clear and strong northerly winds. In fact prior to the widespread take up of roof top PV solar, the grid struggled under precisely those conditions,

http://www.theguardian.com/environment/southern-crossroads/2014/jan/17/heat-wave-australia-record-breaking-climate-change-bushfires-melbourne

Quote

In fact, according to the Clean Energy Council, without rooftop solar "acting to reduce the demand from large-scale power stations, it is very likely that Victoria would have set a new record for power use". So we can thank renewables that there weren't blackouts due to lack of supply.

I think the point is being missed here somehow.
Can I simplify my puzzlement.

If we build enough solar and wind to supply 100%, we know that will not
be sufficient, because the sun does not shine all day & night and there
will always be clouds and we do not live in a continous gale.

So, how many times 100% do we have to build with solar & wind given
our relative large geographical area, given zero losses in transmission ?
Do we have real figures for wind and sunshine for every, say 100sqkm of Australia ?

I have been in my mind going back many years to my work experience
with control systems.

If it is not practical to either establish those figures then no demand techniques could control the network.
Three term control systems require feedback loops to establish
stability, however in this case the primary input (wx) can not be
in a loop & controlled so the problem is basically unsolvable.

Therefore either coal fired power or nuclear is essential as 100% backup.

Further to may last thoughts;
The ERoEI of world coal is continuing to fall and will at some time in
the future become uneconomical to extract.
Australia is in a fortunate position with coal, but if we do not want
to use nuclear we should stop exporting coal and keep it for ourselves
to build whatever new generation systems become available.
We need to stop export because we have no idea how long it will take
to build the new energy systems, it could easily take 50 or 100 years.

With falling GDP we may never be able to afford a fleet of nuclear stations.